Devices are known from the field, which serve to synchronize a magnetic resonance unit with the cardiac rhythm of a patient. In addition to the electrodes of an electrocardiogram device these have an evaluation unit for determining a characteristic trigger time within a cardiac rhythm period of the patient from the electrocardiogram signals of the electrodes. The characteristic trigger time is determined by a simple trigger threshold within the rising or falling edge of the R wave of the electrocardiogram signal. Synchronization serves to prevent motion artifacts, which can be produced, if the magnetic resonance recording takes place in different phases within the periodic motion of the heartbeat.
While the known methods and devices operate sufficiently reliably in the magnetic field-free space, in the magnetic resonance high field a significantly enlarged T wave can result in the ventricle part of the electrocardiogram signal compared with the field-free electrocardiogram due to the magnetohydrodynamic effect acting on the turbulences in the ventricle, so that the amplitude of the T wave can reach the trigger threshold. This significantly impedes automatic identification of the R wave.